Electronic spectroscopy of silver dimer rare gas complexes

Vibrationally resolved electronic spectra are reported for the metal dimer-rare gas complexes Ag₂-Ar and Ag₂-Kr. These spectra are obtained using resonant two-photon photoionization in the energy region near the Ag₂ B←X electronic transition (280-285 nm). Both complexes exhibit extensive activity in three vibrational modes, making it possible to determine vibrational constants, anharmonicities, and cross-mode couplings. An unusual cancellation of factors results in the Kr complex (ω′ _e = 72.6 cm^-1) having nearly the same metal-rare gas stretching frequency as the Ar complex (ω′_e = 73.9 cm^-1). Progressions extending over a significant range of the excited state potential surfaces make it possible to derive the excited state dissociation energies (D′₀ = 755 and 1205 cm^-1 for Ar and Kr, respectively). Combination with the red-shifted electronic state origins yields the corresponding ground state dissociation energies (D″₀ = 275 and 394 cm^-1 for Ar and Kr, respectively). Potential energy surfaces are investigated for excited and ground states of both complexes.